STATE  OF  ILLINOIS 
DEPARTMENT  OF  REGISTRATION  AND  EDUCATION 

DIVISION  OF  THE 
STATE  GEOLOGICAL  SURVEY 

FRANK  W.  DeWOLF,  Chief 
Cooperative  Mining   Series 

BULLETIN  24 

WATER-GAS  OPERATING  METHODS 

WITH  CENTRAL  DISTRICT  BITUMINOUS 

COALS  AS  GENERATOR  FUEL 

A   Summary   of   Experiments   on   a  Commercial   Scale 
A  Prelirnrnary  RepoH 


\V.  A.  IH'XKLKY,  Slau>  Geological    Survey    Division 

mid 
\\\   W.   (IDKI.I..   V.  S.    Bur.. mi    of   Min^d 


ILLINOIS    MINING    rNVKSTIGATIONS 

Prepared  under  a  cooperative  agreement  between  the    Illinois  State  Geological  Survey 

Division,  the  Hncineerinfl  Experiment  Station  of  the  University  of  Illinois, 

and  the  U.  S.    Bureau  of  Mines 


PRINTED   IIY   AITIIOUIIY   OF  TH  K   STATK  <>!•    II.I.IMiis 


URDANA.    ILLINOIS 
1919 


ILLINOIS  MINING  INVESTIGATIONS 
Cooperative    Agreement 
GAS    SECTION 


The  difficulty,  due  to  war  conditions,  of  obtaining  adequate  and 
reliable  delivery  of  eastern  gas-coal  and  of  coke  has  suggested  the 
wider  use  in  gas  manufacture  of  low-sulphur  coal  mined  in  the  central 
district,  comprising  Illinois,  Indiana,  and  western  Kentucky. 

The  needs  of  the  gas  industry,  and  the  desire  of  the  U.  S.  Fuel 
Administration  to  meet  those  needs,  has  led  to  the  appointment  by 
Governor  Frank  O.  Lowden ,  of  a  Technical  Committee  on  Gas, 
By-products,  and  Public  Utilities,  to  act  in  an  advisory  relation.  The 
committee  includes  representatives  of  the  Illinois  Gas  Association,  the 
U.  S.  Bureau  of  Mines,  the  Engineering  Experiment  Station  of  the 
University  of  Illinois,  and  the  State  Geological  Survey  Division  of 
the  Department  of  Registration  and  Education,  State  of  Illinois. 

Previously,  some  studies  of  the  use  of  Illinois  coal  in  retort-gas 
manufacture  and  in  by-product  coke  ovens,  and  of  the  chemical  and 
physical  properties  of  Illinois  coal,  have  been  conducted  under  the 
Illinois  Mining  Investigations,  cooperative  agreement — a  joint  agency 
of  the  U.  S.  Bureau  of  Mines,  the  University  of  Illinois,  and  the 
State  Geological  Survey  Division.  The  continuation  and  expansion  of 
this  work  has  been  recommended  by  the  Technical  Committee  and 
the  Fuel  Administration.  In  response  a  Gas  Section  has  been  created, 
and  experienced  gas  engineers,  chemists,  and  other  specialists  have 
undertaken  a  program  of  experiment  on  a  commercial  scale  to  extend 
the  use  of  central  district  coal  in  water-gas  generators  and  in  gas 
retorts. 

The  results  of  the  investigations  will  be  published,  and,  in  addi- 
-timi_  the  onerators  of  gas  plants  in  the  region  naturally  tributary  to 
.1  will  be  advised  by  the  Technical  Committee,  of 
time  to  time,  and  will  be  urged  to  witness  and  par- 
ts and  to  introduce  in  their  own  plants  new  or 
3  which  will  lessen  the  burden  on  the  railroads, 
les  and  the  coke  ovens  to  meet  the  unprecedented 
e  war. 

suggestions  regarding  the  gas  experiments  should 
as  Section,  Room  305,  Ceramics  Building,  Urbana, 


3  3051  00006  4000 


STATE  OF  ILLINOIS 
DEPARTMENT  OF  REGISTRATION  AND  EDUCATION 

DIVISION  OF  THE 
STATE  GEOLOGICAL  SURVEY 

FRANK  W.  DeWOLF.  Chief 
Cooperative  Mining   Series 

BULLETIN  24 

WATER-GAS  OPERATING  METHODS 

WITH  CENTRAL  DISTRICT  BITUMINOUS 

COALS  AS  GENERATOR  FUEL 

A    Summary   <>t'   Experiments   on   a  Commercial   Scale 
A   Preliminary  Report 


BY 

W    A.   DUNKLEY,  Sun.-  Geological    Survey    Division 

and 

W.  W.  ODKLL,  U.  S.   Bureau   of  Mines 


ILLINOIS    MINING    INVESTIGATIONS 

Prepared  under  a  cooperative  agreement  between  the    Illinois  State  Geological  Survey 

Division,  the  Engineering  Experiment  Station  of  the  University   <>t  Illinois, 

and  the  U.  S.    Bureau  ol  Mines 


PRINTED   UY    AUTHORITY   OF  THE   STATE  OF   ILLINOIS 


URBANA,    ILLINOIS 
1919 


STATE  OF  ILLINOIS 
DEPARTMENT  OF  REGISTRATION  AND  EDUCATION 

DIVISION  OF  THE 

STATE  GEOLOGICAL  SURVEY 

FRANK  W.   DeWOLF,    Chief 

Gommittee  of  the  .Board  of    Natural    Hcsources 
and   Conservation 


Fkaxcis  W.  Shepakdson.  Chairman 

Director   of  Registration    and    Education 

David  Kinley 

Representing  the  President  of  the  Uni- 
versity of  Illinois 


Thomas  C.  Chamberlin 

Geologist 


Schnepp  &  Barnes,  State  Printers 

Springfield,  III. 

1919 

15489— 2  M 


CONTENTS 


PAGE 

Introduction 5 

Problems  and  their  solution 6 

1.  Securing  the   cooperation   of  gas   makers 7 

2.  Use  of  coal  and  coke  mixtures 7 

3.  Selection    of    coal 9 

4.  Control  of  arching  and  caking  of  coal  in  the  generator 10 

5.  Reduction    of    production    capacity    with    coal    fuel,    with    the 

usual  operating  methods 11 

6.     The  blow-run  cycle  for  increasing  capacity 13 

7.  The  blow-run  with  mixed  coal  and  coke 16 

8.  The  air  purge 16 

9.  Smoke  prevention 18 

10.  Prevention  of  sticking  of  valves  caused  by  tar  deposits 20 

11.  Control  of  clinker  from  central  district  coals LM 

Suggestions  for  operating  with  coal  fuel 23 

Conclusions    26 

Acknowledgments    27 


TABLE 


1.     Operating  conditions  and  typical  results  obtained  at  Streator 24 


Digitized  by  the  Internet  Archive 

in  2012  with  funding  from 

University  of  Illinois  Urbana-Champaign 


http://archive.org/details/watergasoperatin24dunk 


WATER-GAS    OPERATING    METHODS    WITH 
CENTRAL  DISTRICT  BITUMINOUS  COALS 
AS    GENERATOR    FUEL-NOTES   ON 
EXPERIMENTS  ON   A  COM- 
MERCIAL SCALE. 

By    W.  A.    Dunkley 
and    W.  W.  OriMl 


INTRODUCTION. 

During  last  July  a  survey  was  made  of  the  gas  plants  of  Illinois 
and  neighboring  states,  to  determine  what  progress  and  economies 
had  been  made  in  the  use  of  the  coals  of  this  region  in  gas  manufac- 
ture. The  facts  learned  from  this  inspection  were  published  in 
Bulletins  2]  and  22  of  this  series,  the  former  bulletin  dealing  with 
the  use  of  these  coals  in  the  manufacture  of  retort-coal  gas,  and  the 
latter  with  their  use  as  water-gas  generator  fuel. 

Although  considerable  progress  had  been  made,  and  some  opera- 
tors were  realizing  a  considerable  saving  from  the  use  of  these  coals. 
it  was  concluded  from  this  inspection  that  much  was  yel  to  be  learned 
about  the  use  of  central  district  coals  in  both  processes,  but  it  was 
thought  that  the  greatest  amount  of  useful  information  could  be  ob- 
tained in  a  short  time  by  further  experimentation  on  the  water-gas 
process.  Accordingly  it  was  decided  to  earn  out  a  series  of  experi 
ments,  on  a  commercial  scale,  to  determine  the  possibilities  of  the 
process,  its  limitations,  available  fuels,  suitable  methods  of  operation, 
and  the  effects  of  many  of  the  variable  conditions  entering  into  water- 
gas  manufacture. 

Through  the  courtesy  of  the  Public  Service  Company  of 
Northern  Illinois,  the  facilities  of  the  Streator  plant  were  extended 
for  experimentation.  This  plant  was  chosen  because  it  is  well 
equipped,  and  because  its  generating  capacity  is  sufficiently  largt 
that  any  errors  in  judgment  or  mistakes  in  the  early  stages  of  the 
experimental  work  would  not  jeopardize  the  gas  supply  to  the  city. 
\lso  the  experiments,  while  conducted  on  a  commercial  scale,  would 
not  involve  the  useless  expenditure  of  as  much  money  on  coals,  some 
of  which  might  prove  unsuitable,  as  would  be  necessary  in  a  larger 
plant. 

5 


b  WATKR-GAS    OPERATING     METHODS 

During  the  course  of  the  experiments,  which  extended  over  a 
period  of  about  four  months,  many  analyses  were  made  of  the  gases 
produced  during  the  -different  stages  of  operation  and  under  various 
operating  conditions.  Other  observations  were  also  made,  and  it  is 
hoped  that  the  publication  and  discussion  of  these  in  a  later  bulletin 
will  throw  more  light  on  the  process  and  lead  to  further  studies. 
The  present  paper  is  preliminary  to  the  main  publication,  and  is 
designed  to  furnish  operating  information  to  the  managers  and  super- 
intendents of  water-gas  plants,  without  going  in  detail  into  the  mass 
of  data  upon  which  the  conclusions  are  based. 

PROBLEMS   AND   THEIR  SOLUTION. 

The  superintendent  who  contemplates  the  use  of  bituminous  coal 
for  water-gas  generator  fuel  is  confronted  by  the  following  problems, 
some  of  which  apply  more  strongly  in  certain  cases  than  in  others: 
the  education  of  gas  makers  in  the  use  of  coal  fuel  and  the  overcoming 
of  their  prejudices  against  it;  the  selection  of  suitable  coal;  the  con- 
trol of  arching  and  caking  in  the  generator;  the  maintenance  of 
production  capacity  with  coal  fuel ;  the  prevention  of  an  excessive 
amount  of  smoke  during  operation;  the  prevention  of  sticking  of 
valves,  due  to  tar  deposits ;  and  the  control  of  clinker  formation. 

Some  of  the  problems  enumerated  could,  perhaps,  be  solved  by 
the  same  methods  in  one  plant  as  in  another,  but  others  require  indi- 
vidual treatment  on  account  of  certain  peculiarities  of  existing  condi- 
tions in  particular  plants.  It  is  obvious  that  the  methods  developed 
in  one  particular  plant  under  one  set  of  conditions  cannot  apply  to  all. 
It  is  the  purpose  of  this  paper  to  discuss  the  principles  governing 
operation  briefly,  to  tell  the  reasons  why  certain  operating  methods 
were  adopted,  and  what  the  results  were  in  the  case  described. 

These  problems  will  be  discussed  under  the  following  heads: 

1.  Securing  the  cooperation  of  gas  makers. 

2.  Use  of  coal  and  coke  mixtures. 

3.  Selection  of  coal. 

4.  Control  of  arching  and  caking  of  coal  in  the  generator. 

5.  Reduction  of  production  capacity  with  coal  fuel,  with  the  usual 

operating  methods. 

6.  The  blow-run  cycle  for  increasing  capacity. 

7.  The  blow-run  with  mixed  coal  and  coke. 

8.  The  air  purge. 

9.  Smoke  prevention. 

10.  Prevention  of  sticking  of  valves. 

1 1.  Control  of  clinker. 


WATER-GAS    OPERATING    METHODS  7 

1.     Securing  the  Cooperation  of  Gas  Makers 

Of  the  problems  mentioned,  the  first  is  often  the  most  difficult 
one  to  solve.  The  uncertainty  of  the  results  to  be  obtained  with  an 
unknown  fuel,  the  lack  of  a  financial  incentive  to  undertake  some- 
thing which  is  new  and  untried,  and  which  may  lead  to  difficulties  or 
inconveniences,  are  sufficient  to  prejudice  many  gas  makers,  even 
before  a  trial  is  made. 

The  superintendent  who  is  about  to  try  a  new  fuel,  and  especially 
a  fuel  so  different  from  the  customary  as  is  bituminous  coal,  must  fit 
his  method  of  attack  to  the  temperament  of  his  operators.  Different 
methods  must  be  used  in  different  cases.  It  must  be  realized  that  the 
cooperation  of  the  gas  maker  must  be  obtained  for  good  results.  A 
good  gas  maker  senses  the  behavior  of  his  machine  in  a  manner  in- 
comprehensible to  the  mere  technical  man,  and  this  peculiar  under- 
standing can  be  utilized  to  advantage  if  at  the  same  time  the  more 
visible  conditions  are  kept  sight  of  carefully. 

It  is  not  the  purpose  of  this  paper  to  tell  the  superintendent  how 
to  handle  his  men,  but  merely  to  suggest  how  essential  to  success  is 
their  cooperation.  It  is  believed  that  tin's  can  be  obtained  in  any  way 
which  makes  them  feel  that  it  is  to  their  interest  to  succeed,  or  that 
they  are  believed  to  be  capable  of  accomplishing  something  out  of 
the  ordinary. 

2.    Use  of  Coal  and  Coke  Mixture 

In  starting  the  use  of  coal  fuel  in  a  plant  where  it  has  never  been 
tried,  the  writers  are  of  the  opinion  that  it  is  preferable  for  operators 
to  accustom  their  gas  makers  gradually  to  the  new  conditions  by 
running  for  a  time  with  a  mixture  of  coal  and  coke,  and  gradually 
increasing  the  percentage  of  coal.  In  this  way  the  operating  condi- 
tions may  be  changed  gradually  and  loo  per  cent  coal  used  eventually 
with  little  difficulty. 

In  case  the  production  capacity  of  a  plant  is  barely  sufficient  tO' 
carry  the  load  with  straight  coal,  it  will  usually  be  found  that  the 
capacity  may  be  increased  materially,  cither  by  the  use  of  a  coal  and 
coke  mixture,  or,  if  plant  conditions  will  permit,  by  the  adoption  of 
the  blow-run  cycle  which  will  be  described  later.  The  mixture  of  a 
small  percentage  of  coke  with  the  coal  makes  the  fire  more  permeable 
to  the  blast,  thereby  permitting  more  air  to  pass  through  the  lire  in. 
a  given  time  with  the  same  blast  pressure.  In  the  Streator  tots  about 
12  per  cent  more  blast  passed  the  fire  with  a  mixture  containing  15 
per  cent  coal  than  with  100  per  cent  coal.  This  practice  results  in  a 
higher  fuel-bed  temperature  and  a  consequent  larger  make  during 
the  steam  run. 


8  WATER-GAS    OPERATING    METHODS 

Usually  it  is  not  necessary  to  begin  with  a  very  small  percentage 
of  coal.  A  half  and  half  mixture  can  usually  be  employed  from  the 
start  without  difficulty.  Since  coke  is  considerably  more  expensive 
than  coal,  the  operator  who  desires  to  make  as  great  a  saving  as  pos- 
sible consistent  with  his  operating  conditions,  will  finally  use  the 
smallest  amount  of  coke  in  the  mixture  that  will  permit  him  to  get 
the  necessary  capacity  from  his  machine.  In  the  tests  at  Streator  the 
results  over  a  long  period  indicated  that  a  larger  output  per  hour  of 
operating  time  could  be  obtained  from  a  mixture  containing  70  to  SO 
per  cent  coal  than  from  mixtures  containing  either  more  or  less  coal. 

While  mixtures  of  coal  and  coke  offer  some  advantages  in  in- 
creasing machine  capacity,  somewhat  more  oil  is  required  to  maintain 
a  given  heating  value  than  with  straight  coal.  This  increase  may 
.amount  to  between  0.1  and  0.2  gallon  of  oil  per  1,000  cubic  feet  of 
finished  gas  with  25  per  cent  of  coke  in  the  mixture.  The  generator 
fuel  during  the  Streator  test  was*  about  three  to  four  pounds  per  1 ,000 
iess"  with  the  mixture  than  with  straight  coal.  However,  on  account 
of  the  different  rates  of  burning  of  coal  and  coke  during  lay-over 
periods,  this  difference  might  not  be  found  in  a  plant  operating  practi- 
cally continuously.  The  steam  per  1,000  cubic  feet  was  about  five 
pounds  greater  with  the  mixed  fuel. 

A  coal  and  coke  mixture,  without  a  blow-run,  may  be  used  in 
one  of  two  ways,  according  to  the  results  desired.  All  the  coke  may 
be  charged  into  the  machine  during  the  first  part  of  the  day's  run,  or 
it  may  be  mixed  with  the  coal  in  each  charge.  The  first  method  gives 
a  quicker  start,  and  the  subsequent  running  is  practically  on  straight 
coal.  With  the  other  method  the  start  is. not  so  quick,  but  the  average 
liourly  make  will  usually  be  greater  and  more  uniform.  Or  the 
operator  may  combine  the  two  methods,  making  the  first  charges 
chiefly  coke  and  the  later  charges  chiefly  coal.  Which  method  is  de- 
sirable will  probably  depend  upon  the  local  conditions,  as  length  of 
operating  time,  for  example. 


WATER-GAS    OPERATING    METHODS  9 

3.     Selection  of  Coal 

In  selecting  a  central  district  coal  for  use  as  generator  fuel  many 
of  the  same  considerations  apply  as  with  other  fuels  for  this  purpose. 
The  coal  should  not  break  up  too  much  on  handling  and  it  should  be 
as  free  as  possible  from  ash.  The  sulphur  content  is  also  a  very  im- 
portant consideration.  While  analyses  of  the  coals  used  in  Streator 
are  not  yet  completed,  the  indications  are  that  at  least  one-fourth  of 
the  sulphur  present  in  the  coal  passes  into  the  blue  gas.  For  example, 
a  coal  containing  about  1.57  per  cent  S  gave  155  grains  H2S  per  100 
cubic  feet  in  the  blue  gas.  The  Texas  oil  used  brought  this  up  to  200 
grains  in  the  unpurified  carburetted  gas.  Probably  the  form  in  which 
the  sulphur  is  present  in  the  coal  has  a  marked  effect  on  the  amount 
transmitted  to  the  gas.  It  is  hoped  that  a  further  study  of  this  rela- 
tion may  be  discussed  in  the  main  report.  In  general  it  seems  prob- 
able that  any  plant  which  is  not  equipped  to  purify  raw  gas  containing 
more  than  200  grains  of  H2S  per  100  cubic  feet  at  the  average  rate 
of  purification,  should  insist  on  a  sulphur  content  not  exceeding  1.50 
per  cent  in  the  delivered  coal.  Bulletin  No.  23  of  this  series  gives  a 
list  of  the  mines  of  the  central  district  which  could  probably  furnish 
coal  meeting  the  above  condition. 

As  with  the  other  fuels  the  size  of  coal  required  for  water-gas 
manufacture  is  important.  Since  nearly  all  central  district  coals  show 
the  coking  property  in  varying  degrees,  it  is  not  possible  to  prescribe 
one  best  size  for  all  coals. 

The  stronger  the  coking  property  of  a  coal,  the  greater  is  the 
tendency  for  the  lumps  to  mat  together  in  the  fire.  The  effect  of  this 
is  similar  to  the  conditions  existing  when  a  coal  containing  consider- 
able slack  is  used.  In  the  experiments  at  Streator,  large  egg  size  (4  to 
6  inches)  gave  satisfactory  results.  Some  of  the  coals  used  broke  up 
more  readily  than  others,  so  that  there  was  considerable  slack  present 
in  some  cases.  While  under  favorable  conditions  of  blast  pressure, 
etc.,  it  is  possible  to  use  coal  containing  considerable  slack,  its  effect 
in  obstructing  the  passage  of  air  through  the  fire  is  detrimental ;  and 
careful  forking  and  the  avoidance  of  unnecessary  breakage  in 
handling  are  therefore  recommended. 

Some  central  district  coals  tend  to  disintegrate  somewhat  during 
storage,  especially  if  exposed  to  the  weather.  Since  the  size  is  of 
considerable  importance  in  water-gas  operation,  it  seems  inadvisable 
to  store  coal  for  this  purpose  longer  than  necessary  to  maintain  an 
adequate  stock.  When  necessary  to  store  such  coal,  it  may  be  ad- 
visable to  purchase  a  larger  size  than  otherwise  required,  in  order  to 
make  due  allowance  for  disintegration  and  breakage.  The  larger 
sizes  are  also  less  liable  to  spontaneous  ignition. 


10  WATER-GAS    OPERATING    METHODS 

4.     Control  of  Arching  and  Caking  of  Coal  in  the  Generator 

For  successful  operation  with  coal,  the  method  of  procedure 
must  be  different  from  that  with  coke,  else  trouble  is  likely  to  be 
speedily  encountered.  Coke  in  the  generator  presents  a  porous  loose 
mass  to  the  passage  of  air  and  gases  through  the  fire,  while  on  the 
other  hand,  most  bituminous  coals  tend  when  freshly  charged  to  cake 
and  run  together.  This  caking,  if  excessive,  is  evidenced  by  an  in- 
crease in  the  blast  pressure  under  the  grate,  other  conditions  remain- 
ing the  same,  and  if  the  set  is  equipped  with  an  air  meter  in  the 
generator  blast  line,  a  decided  decrease  in  the  amount  of  air  going 
through  the  fire  will  be  indicated  soon  after  making  a  fresh  coaling. 
This  is  especially  true  when  excessively  heavy  charges  are  made.  It 
is  frequently  customary  in  plants  operating  with  coke  to  make  at  the 
beginning  of  the  day's  run,  one  or  more  fuel  charges  of  two  or  three 
times  the  size  of  the  normal  running  charge  which  is  made  after  the 
fuel  bed  is  up  to  its  usual  operating  depth.  With  the  usual  bitum- 
inous coal  this  procedure  would  almost  certainly  lead  to  trouble.  In 
general,  it  may  be  said  that  large  egg-size  coal,  even  with  the  caking 
controlled,  offers  more  resistance  to  the  passage  of  air  than  does 
coke,  and  the  addition  of  a  large  charge  of  green  coal  causes  an  ex- 
cessive increase  in  this  resistance.  The  fuel  on  caking  forms  a  nearly 
impenetrable  arch  over  the  fire,  which  hinders  the  passage  of  air. 
This  slows  up  the  combustion  during  the  blast  period,  decreases  the 
temperature  of  the  fuel  bed,  and  results  in  a  great  decrease  in  the 
amount  of  gas  produced  during  the  run  period.  This  arching  fre- 
quently remains  in  the  place  where  formed,  even  after  the  already 
coked  fuel  beneath  it  has  burned  away,  leaving  a  hollow  space  be- 
tween. The  arching  may  be  so  tenacious  that  it  is  necessary  to  break 
it  up  with  bars  before  another  coal  charge  can  be  added.  This,  of 
course,  is  unwelcome  labor,  even  were  it  not  an  indication  of  an 
unhealthy  operating  condition. 

The  prevention  of  arching  can  be  readily  accomplished  by  mak- 
ing charges  of  normal  size  and  with  greater  frequency  during  the 
early  part  of  the  day's  run.  At  Streator  it  was  the  practice  to  make 
one  run  in  the  morning  before  coaling; 'the  reason  for  this  will  be 
discussed  later.  A  normal  charge  was  added  after  the  first  run, 
another  after  the  third  run,  and  this  method  was  continued  until  the 
fire  was  up  to  its  usual  operating  level  even  with  the  bottom  of  the 
take-off  connection,  as  with  coke.  After  this  the  depth  of  lire  was 
maintained  by  normal  size  charges  about  35  to  45  minutes  apart.  The 
weight  of  these  charges  was  about  the  same  as  the  weight  of   the 


VVATEE-GAS    OPERATING    METHODS  11 

normal  charge  when  using  coke.  It  was  found  that  by  this  method  of 
charging  the  resistance  to  the  passage  of  air  through  the  fire  was  not 
excessive,  the  fire  burned  down  uniformly,  and  there  was  no  arching, 
and  consequently  barring  down  was  no  longer  necessary.  Where  a 
coal  with  very  strong  coking  properties  is  used  and  arching  persists 
even  under  the  above  conditions,  the  difficulty  can  be  remedied  by 
making  smaller  but  more  frequent  charges,  though  this  necessitates 
opening  the  generator  more  frequently,  and  causes  a  certain  loss  of 
operating  time.  In  many  plants  the  loss  of  time  during  coaling  is 
excessive  and  could  be  considerably  reduced  by  carefully  arranging 
the  movements  of  the  various  men  participating  in  the  operation.  It 
will  usually  be  found,  however,  that  the  time  required  for  coaling  with 
central  district  coals  is  no  greater  than  with  coke. 

It  was  formerly  believed  by  some  operators  that  in  using  bitum- 
inous coal  as  generator  fuel,  the  volatile  matter  would  be  largely 
driven  off  from  a  fresh  charge  during  the  first  blast  after  coaling. 
Contrary  to  this,  it  is  found  that  the  surface  of  the  fuel  bed  remains 
fairly  cool  from  charge  to  charge.  The  surface  of  a  charge  has  not 
been  entirely  converted  into  coke  when  the  next  charge  is  added.  The 
rate  of  conversion  into  coke  will  of  course  depend  upon  the  tempera- 
ture obtained  in  the  generator  which  in  turn  is  dependent  upon  the 
amount  of  air  passed  through  the  fire  during  the  blast  period  and 
the  amount  of  steam  used  during  the  run.  (  hi  out'  occasion  a  6-inch 
lump  of  coal  removed  from  the  fire  just  before  making  a  fresh  charge 
showed  about  -y\  inch  of  coking  on  each  face,  perpendicular  to  the 
lamination^  of  the  coal;  while  the  other  two  faces  had  coked  to  a 
depth  of  about  j4  inch. 

The  fact  that  the  surface  of  the  fuel  usually  remains  relatively 
cool  often  causes  delay  in  the  ignition  of  the  generator  gases  when 
the  lid  is  opened  for  charging.  These  gases  are  usually  combustible 
and  a  continuously  burning  pilot  light  or  some  form  of  torch  kept 
handy  for  igniting  them  will  avoid  any  unnecessary  delay  caused  by 
their  failure  to  ignite'  spontaneously.  As  in  the  ease  with  coke  fuel, 
care  should  be  observed  that  the  gases  are  ignited  before  attempting 
to  charge. 

5.     Reduction  of   Production  Capacity  \\ 'mi   Coal   Fuel,  With 
the  Usual  Operating  Methods 

The  chief  difficult}-  encountered  by  man}-  gas  companies,  especi- 
ally the  larger  ones,  in  using  bituminous  coal  for  generator  fuel  in 
place  of  coke  is  the  decrease  in  production  capacity  ordinarily  exper- 
ienced with  coal.  Various  operators  have  reported  a  decrease  of  25 
•or  30  per  cent  in  the  possible  output  of  the  plant  when  using  coal,  as 


12  WATER-GAS    OPERATING    METHODS 

compared  with  coke.  One  reason  for  this  decrease  seems  to  lie  in 
the  difference  of  the  resistance  of  the  two  fuels  to  the  passage  of  air 
under  the  same  blast  conditions.  The  rate  of  combustion  of  the  fuel, 
and  therefore  the  rate  at  which  it  acquires  a  gas-making  temperature, 
seems  to  be  roughly  proportional  to  the  amount  of  air  passing  through 
the  fire  in  a  given  time.  If  the  air  volume  passing  is  increased  by 
increasing  the  air  pressure,  then  the  combustion  is  more  rapid,  and 
the  fuel  bed  is  brought  more  quickly  to  the  proper  temperature  for 
decomposing  steam.  In  most  gas  plants  the  blowing  capacity  is 
limited,  and  the  initial  pressure  at  the  base  of  the  generator  is  like- 
wise limited  by  the  type  of  blower  used.  Consequently,  since  the  coal 
fuel  bed  offers  more  resistance  to  the  passage  of  air  through  the  fire 
than  does  coke,  more  air  is  transmitted  at  the  pressure  available  with 
a  coke  fire  than  with  coal,  the  combustion  is  more  rapid,  and  during 
the  run  the  gas  production  is  greater  with  coke.  If  it  were  possible 
to  force  the  same  volume  of  air  through  the  coal  fire  in  a  given  time, 
it  seems  likely  that  the  volume  of  gas  produced  during  a  given  time 
would  more  nearly  approach  that  with  coke. 

Under  the  usual  operating  conditions,  therefore,  it  will  usually 
take  a  blow  period  longer  in  proportion  to  the  length  of  steam  run 
with  coal  than  with  coke,  in  order  to  bring  the  fuel  up  to  the  same 
working  temperature.  On  account  of  the  greater  amount  of  volatile 
matter  in  the  coal,  the  amount  of  combustible  gas  given  off  during 
the  relatively  longer  blow  period  is  more  than  sufficient  to  maintain 
the  requisite  temperatures  in  the  carburetor  and  superheater ;  conse- 
quently the  length  of  blast  period  which  is  suitable  for  the  generator 
overheats  the  other  chambers,  if  the  gas  is  entirely  burned  in  them, 
or  necessitates  the  burning  of  considerable  gas  at  the  stack.  Either 
condition  is  undesirable  and  wasteful.  With  this  condition  of  an  ex- 
cessive production  of  combustible  generator  blast  gases,  it  is  often 
found  impossible  to  burn  them  in  the  set  even  with  the  carburetor 
blast  valve  wide  open  unless  the  volume  of  these  gases  is  decreased 
by  partially  closing  the  generator  blast  valve,  or  the  fuel  bed  is  unduly 
cooled  by  excessive  use  of  steam  during  the  steam  run.  In  either  case, 
however,  the  generator  will  not  attain  the  desired  temperature  so 
quickly.  In  some  plants  where  there  is  an  excess  blowing  capacity, 
it  may  be  advisable  to  cool  the  carburetor  and  superheater  by  over- 
blowing them  rather  than  to  underblow  or  oversteam  the  generator. 
By  any  of  these  methods,  however,  capacity  can  only  be  obtained  by 
sacrificing  a  considerable  amount  of  combustible  gas,  resulting  in  a 
waste  of  fuel. 


WATER-GAS    OPERATING    METHODS  13 

6.     The  Blow-run  Cycle  for  Increasing  Capacity 

A  system  of  operation  was  tried  out  and  used  successfully,  which 
enables  a  more  thorough  heating  of  the  generator,  yet  retards  the 
overheating  of  the  other  chambers  and  saves  some  of  the  volatile 
matter  which  would  otherwise  be  wasted.  To  accomplish  this  the 
fire  was  usually  blasted  in  the  regular  way  for  three  minutes,  the 
blast  pressure  being  about  17  to  19  inches  water  pressure  under  the 
grate,  when  both  the  generator  and  carburetor  blast  valves  were  open. 
At  the  end  of  this  blast  period  the  carburetor  blast  valve  (and  super- 
heater blast  valve  when  used)  were  closed.  The  stack  cap  was  closed, 
and  a  blow  varying  in  length  from  15  to  30  seconds  was  made  through 
into  the  relief  holder.  At  the  end  of  this  "blow-run",  as  it  will  be 
herein  designated,  the  generator  blast  valve  was  closed,  the  steam 
and  oil  turned  on,  and  the  steam  run  was  made  in  the  usual  way.  The 
effect  of  this  additional  l/^-  to  ^-minute  blast  was  beneficial,  since  it 
brought  the  fire  up  to  a  better  gas-making  temperature,  and  yet  did 
not  heat  up  the  other  chambers  to  any  appreciable  degree,  Mnce  only 
the  sensible  heat  in  the  blow-run  gases  was  carried  into  those  cham- 
bers which  were  probably  at  a  higher  temperature  than  the  gases,  the 
temperature  of  which  varies  from  run  to  run.  Since  no  combustion 
was  taking  place  in  them,  the  temperature  remained  stationary,  or 
possibly  decreased  slightly,  which  seemed  to  have  a  beneficial  effect 
on  the  subsequent  oil  cracking.  The  higher  temperature  in  the  fuel 
bed  obtained  by  this  method  resulted  in  a  richer  blue  gas  being  made 
during  the  steam  run  and  this  helped  to  compensate  for  the  relatively 
low  quality  of  the  gas  made  during  the  actual  blow-run  period,  though 
of  course  some  additional  oil  per  1,000  cubic  feet  of  gas  was  required 
to  bring  the  mixture  of  blue  gas  and  blow-run  gas  up  to  standard, 
beyond  that  required  per  1,000  cubic  feet  of  straight  blue  gas  made 
by  the  usual  method  with  coal  fuel. 

The  volume  of  gas  formed  during  the  blow-run  when  the  blast 
pressure  and  back  pressure  on  the  set  were  normal  was  about  10  pet- 
cent  to  20  per  cent  of  the  total  make  of  carburetted  gas.  In  composi- 
tion the  blow-run  gas  was  a  rich  producer  gas,1  having  a  calculated 
heating  value  of  about  155  B.  t.  u.,  or  about  45  per  cent  of  the  heating 
value  of  the  blue  gas  formed  during  the  steam  run.  Jt  contained  about 
60  per  cent  of  nitrogen  and  with  the  nitrogen  present  in  the  bine  gas, 
resulted  in  about  14  to  20  per  cent  of  nitrogen  in  the  finished  car- 
buretted gas.     It  should  be  noted,  however,  that  while  the  blow-run 


1  Technically,  the  term  ;iii--^;is  is  used  as  ;ippli<'<l   i<>  Hi''  gas   from  a    producer 
when  air  alone  without  steam  is  blown  through  the  fire 


14  •  WATER-GAS    OPERATING    METHODS 

cycle  introduces  some  nitrogen  into  the  gas,  the  oxygen  which  ac- 
companied this  nitrogen  in  the  air,  has  been  entirely  removed  by  the 
hot  fuel  bed  and  converted  chiefly  into  carbon  monoxide,  a  combus- 
tible gas.  Therefore  there  is  no  chance  of  forming  an  explosive  mix- 
ture in  the  holder  by  this  method  since  there  is  no  oxygen  present  in 
the  finished  gas.  Since  the  addition  of  nitrogen  is  compensated  for  by 
the  use  of  more  oil  and  by  the  formation  of  richer  blue  gas  during 
the  steam  run,  so  that  the  heating  value  of  the  gas  will  be  the  same  as 
it  would  with  the  usual  methods,  there  appears  to  be  little  real  reason 
for  objection  to  the  presence  of  this  additional  nitrogen.  One  of  the 
chief  arguments  advanced  against  the  presence  of  inert  constituents 
in  the  gas  is  that  their  presence  reduces  the  temperature  possible  of 
attainment  when  the  gas  is  burned  since  it  is  necessary  to  heat  this 
inert  material  to  the  temperature  at  which  the  combustion  products 
are  discharged  from  the  appliance  in  which  the  gas  is  burned.  Com- 
putations from  the  analyses  of  typical  gases  produced  by  the  blow- 
run  and  by  the  usual  method,  show  that  the  difference  between  the 
nominal  flame  temperatures  in  the  two  cases  is  so  small  that  it  would 
be  practically  negligible  even  in  high  temperature  industrial  appliances 
and  especially  so  in  ordinary  domestic  appliances  where  the  tempera- 
tures to  be  attained  in  the  materials  to  be  heated  are  relatively  low. 

Since  with  this  method  more  oil  is  required  per  run,  a  greater 
amount  of  heat  is  absorbed  from  the  carburetor  and  superheater  dur- 
ing this  period.  Thus  the  gas  maker  is  permitted  to  burn  more  of  the 
combustible  blast  gas  in  the  set  without  danger  of  overheating  the 
checker  work.  This  method  also  enables  the  operator  to  increase  the 
capacity  of  his  machine  from  20  to  30  per  cent  over  what  he  could 
obtain  from  coal  without  this  cycle,  and  if  the  operation  is  properly 
timed  so  that  the  blow-run  is  hot  made  of  excessive  length  (not  ex- 
ceeding 30  seconds  with  normal  air  blast  and  back  pressure  condi- 
tions) a  distinct  advantage  should  be  realized.  The  amount  of  gas 
oil  which  must  be  used  to  carburet  the  blue  gas  up  to  the  required 
standard,  will  vary  in  different  plants  under  different  conditions.  The 
quality  of  the  oil  used,  the  B.  t.  u.  standard  maintained,  the  weather 
conditions,  the  condition  of  the  checker  work  in  the  carburetor  and 
superheater,  the  daily  operating  time,  and  many  other  conditions  affect 
oil  efficiency.  In  the  Streator  plant,  under  the  conditions  existing  in 
the  manufacturing  and  distribution  systems,  during  the  late  summer, 
fall  and  early  winter,  the  Texas  oil  required  to  maintain  565  B.  t.  u.  a 
mile  from  the  plant  amounted  to  between  3.00  and  3.10  gallons  per 
1,000  cubic  feet  of  gas  made  (corrected)  with  this  cycle.  During  the 
warmer  part  of  the  test  period,  the  amount  was  somewhat  less  than 


WATER-GAS    OPERATING    METHODS  15 

this  and  had  more  severe  weather  been  experienced,  the  amount  of 
oil  used  would  doubtless  have  been  somewhat  higher.  The  writers 
of  this  paper  do  not  maintain  that  these  oil  results  could  be  duplicated 
in  all  cases  or  with  inferior  oils.  Large  plants  which  are  unable  to 
obtain  all  their  oil  from  one  source  and  must  at  times  use  mixtures 
containing  inferior  oils  would  doubtless  find  it  difficult  if  not  impos- 
sible to  maintain  the  required  standard  of  quality  with  this  amount 
of  oil,  even  with  weather  and  other  conditions  as  favorable  as  those 
obtaining  at  Streator  during  the  experiments.  On  the  other  hand,  a 
plant  operating  full  time  with  all  other  conditions  favorable  might 
realize  even  better  results.  The  figures  stated  are  simply  for  compar- 
ative purposes  under  the  conditions  with  which  they-  were  obtained. 
The  blow-run  gives  the  operator  a  rather  flexible  means  of  con- 
trolling the  heat  balance  in  his  machine.  If  the  temperatures  in  the 
carburetor  and  superheater  tend  to  increase  while  the  generator  cools 
somewhat  a  little  longer  blow-run  for  a  few  runs,  in  addition  to  the 
regular  blasting  time,  increases  the  temperature  in  the  generator,  and, 
due  to  the  fact  that  the  increased  volume  of  gas  thus  produced  will 
require  the  use  of  more  oil  per  run,  the  result  is  a  decrease  in  the 
temperatures  prevailing  in  the  carburetor  and  superheater.  Similarly 
decreasing  the  length  of  the  blow-run  has  the  opposite  effect.  In  case 
the  temperatures  of  the  carburetor  and  superheater  arc  unduly  low 
when  the  blow-run  cycle  is  being  used,  it  should  be  ascertained 
whether  these  chambers  are  being  overblown  during  the  blasting 
period.  It  may  also  be  advantageous  to  make-  the  blow  period  a  little 
longer  in  some  eases  rather  than  to  reduce  the  length  of  the  blow-run. 
The  advantages  derived  from  the  blow-run  may  be  summed  up  as 
follows:  It  enables  the  operator  to  heat  up  his  generator  without 
wasting  the  combustible  gases  produced  during  the  last  part  of  the 
blow,  or  overheating  his  carburetor  and  superheater  in  an  effort  to 
burn  these  gases  completely  within  the  set.  It  enables  Him  to  m 
more  and  better  gas  during  the  steam  run  on  account  of  the  higher 
temperature  of  his  generator  at  the  end  of  the  blow-run.  It  saves  for 
use  a  volume  of  blow-run  gas  equal  to  about  20  per  cent  of  the  volume 
of  blue  gas  made  during  the  run,  and  to  increase  his  make  per  run  by 
about  20  to  30  per  cent.  The  indications  from  the  tests  made  have 
been  that  the  amount  of  generator  fuel  used  per  L,000  cubic  feet  of 
gas  made  is  decidedly  lower  with  this  cycle  than  when  no  blow-run 
is  used.  This  naturally  follows  since  the  air  used  during  the  blow- 
run  serves  the  double  purpose  of  heating  the  generator  and  increasing 
the  total  volume  of  gas  made.  Considerably  less  steam  is  required 
per  1. ')()()  cubic  feet  of  gas  made  when  employing  the  blow-run.     Care 


16  WATER-GAS    OPERATING    METHODS 

should  be  exercised  where  this  cycle  is  used  that  it  be  used  with 
moderation,  and  where  so  used  it  is  believed  that  it  will  be  very  ad- 
vantageous, especially  in  plants  which  are  operating  near  to  capacity 
with  coke  fuel  and  could  not  make  enough  gas  with  coal  fuel  by  the 
usual  methods. 

Even  in  plants  which  are  not  working  near  to  capacity,  the  blow- 
run  cycle  may  be  of  economical  advantage  over  the  use  of  the  usual 
method,  with  coal  fuel.  Although  a  little  more  oil  is  required  to 
carburet  the  gas  produced  from  straight  coal  with  the  blow-run 
method  of  operation  than  without  the  blow-run,  the  shorter  running 
time  to  produce  a  given  amount  of  gas  results  in  less  wear  and  tear 
on  the  machine  and  gives  the  operator  more  time  to  make  necessary 
plant  repairs  with  the  same  operating  force. 

7.     The  Blow-Rux  With  Mixed  Coal  and  Coke 

In  case  a  still  greater  output  capacity  is  desired  than  can  be 
furnished  with  straight  coal  with  the  blow-run  cycle,  this  may  be 
obtained  by  the  use  of  a  small  percentage  of  coke,  up  to  say  25  per 
cent,  together  with  a  blow-run  of  suitable  length,  depending  upon  the 
air  blast  available,  quality  of  gas  to  be  maintained,  and  hourly  make 
desired.  During  a  run  of  a  few  days  at  the  Streator  plant  with  25 
per  cent  coke  and  a  30-second  blow-run,  the  hourly  output  was  in- 
creased about  6  per  cent  over  that  obtained  during  the  days  immedi- 
ately preceding,  when  100  per  cent  coal  was  used.  The  blast  pressure 
was  practically  the  same  in  both  cases.  During  the  few  days  that 
this  combination  of  conditions  was  tried,  there  was  no  perceptible 
increase  in  the  amount  of  oil  used  per  1,000  cubic  feet  of  gas  to 
maintain  practically  the  same  heating  value. 

8.     The  Air  Purge 

A  form  of  blow-run,  commonly  called  an  "air  purge,"  has  been  used 
in  some  of  the  plants  visited,  but  in  all  cases  it  has  followed  the  steam 
run  instead  of  preceding  it.  The  disadvantage  of  this  procedure  will  be 
readily  seen  when  the  analyses  of  the  blast  gases  produced  just  before 
and  just  after  the  run  are  compared.  The  blast  gases  immediately 
after  the  run  are  very  lean,  since  the  fire  is  cold.  They  contain  usually 
from  seven  to  eight  times  as  much  carbon  dioxide  and  nearly  25'  per 
cent  more  nitrogen,  and  have  a  heating  value  approximately  one-half 
of  the  heating  value  of  the  gases  of  a  blow-run  following  the  regular 
blast  period.  However  it  seems  advisable  to  purge  the  set  of  gas  by 
means  of  the  air  blast,  after  every  run,  if  the  purge  time  is  made  so 
short  that  practically  no  blast  gas  is  blown  into  the  holder.  While 
it  is  usually  presumed  that  at  the  end  of  a  run  the  gas  left  in  the 


WATER-GAS    OPERATING    METHODS  17 

carburetor  and  superheater  is  a  lean  blue  gas,  quite  often  there  is  an 
appreciable  amount  of  oil  gas  present  also,  as  well  as  some  volatile 
matter  from  the  coal,  which  it  is  desirable  to  save.  The  quality  of 
this  gas  depends  primarily  on  the  amount  of  oil  added  during  the  run, 
the  time  during  which  oil  is  admitted,  the  length  of  the  run  after  all 
the  oil  has  been  admitted,  the  temperature  of  the  fuel  in  the  generator, 
and  the  amount  of  steam  used  during  the  run.  The  time  required 
for  this  air  purge  will  vary  from  5  to  15  seconds,  and  is  chiefly  de- 
pendent on  the  back  pressure.  When  this  back  pressure  is  excessive 
the  time  required  to  purge  the  set  may  be  so  great  as  to  more  than  off- 
set the  advantage  of  an  increase  in  volume  of  gas  made,  which  is 
realized  when  using  the  purge  under  more  favorable  conditions.  The 
proper  length  of  air  purging  time  is  best  determined  by  watching  the 
stack  when  the  lid  is  raised  after  a  run,  and  observing  the  flame.  The 
purging  time  may  be  gradually  increased  until  it  is  observed  that  most 
of  the  rich  gas  has  been  driven  out  of  the  set  previous  to  raising  the 
stack  lid. 

The  advantages  of 'the  blow-run  cycle  in  increasing  the  producing 
capacity  of  the  set,  and  in  saving  fuel,  have  been  discussed,  it  being 
assumed  that  in  a  majority  of  plants  there  would  be  no  mechanical 
difficulties  to  be  overcome.  This  is  not,  however,  the  case  in  some 
plants,  especially  the  larger  city  stations.  Owing  to  the  rapid  growth 
of  the  gas  output  in  some  communities,  several  additional  gas  sets 
have  been  added  to  the  original  installation,  without  corresponding 
increases  in  the  connecting  mains  joining  the  sets  to  the  relief  holders 
and  intermediate  apparatus.  It  is  not  uncommon  to  find  a  half  dozen 
sets  making  gas  into  a  main  which  was  originally  designed  for  not 
more  than  half  that  number,  and  frequently  the  pressure  in  the  con- 
necting lines  may  mount  up  to  30  or  40  inches  of  water.  Since  the 
blast  pressure  supplied  by  the  blowers  at  these  plants  is  seldom  in 
excess  of  20  to  24  inches  of  water,  it  is  evident  that  any  attempt  to 
make  a  blow-run  against  such  a  pressure  would  be  futile.  It  is  be- 
yond the  province  of  this  paper  to  discuss  the  soundness  of  the 
engineering  policy  which  has  led  to  such  pressures  in  the  collecting 
mains.  It  has  doubtless  been  dictated  by  economic  consideration,  and 
the  fact  which  must  be  faced  is  that  such  conditions  exist.  If  it  is 
decided  by  a  company  that  the  use  of  coal  with  the  blow-run  cycle  is 
feasible,  it  is  an  economic  problem  to  decide  what  expenditure  is 
justified  to  relieve  such  conditions,  in  other  words,  whether  the  savins: 
from  the  use  of  coal  would  be  sufficient  to  warrant  the  changes. 

Another  less  serious  mechanical  difficulty  will  be  found  in  plants 
which   are   equipped   with   certain    interlocking    safety    devices    which 


18  WATER-GAS    OPERATING    METHODS 

make  the  operation  of  the  various  valves  follow  a  predetermined 
sequence.  These  interlocking  systems  are  quite  extensive  and  com- 
plicated in  some  plants  while  in  others  there  may  be  but  a  single 
interlocking  device  or  none  at  all.  One  type  of  gas  machine  in  very 
common  use  has  a  butterfly  valve  in  the  blast  main  which  closes  when 
the  stack  lid  closes.  It  would  not,  of  course,  be  possible  to  make  a 
blow-run  with  this  device  in  operation,  but  fortunately  -it  is  easily 
disconnected  and  arranged  so  that  the  butterfly  valve  will  be  perm- 
anently open,  the  smaller  butterfly  valve  in  the  vent  to  the  air  re- 
maining permanently  closed.  While  it  is  not  desired  to  belittle  these 
safety  devices,  it  is  not  believed  that  with  the  usual  care  in  operation 
the  chances  of  damage  to  the  blast  main  will  be  greatly  increased, 
especially  if  "tell-tale"  pipes  are  led  from  the  inlet  sides  of  the  vari- 
ous blast  valves  to  the  gas-maker's  station,  and  the  usual  cardboard 
heads  are  installed  in  the  ends  of  blast  mains  to  protect  them  in  case 
of  explosion. 

Since  the  sequence  of  operations  is  different  with  the  blow-run 
cycle  than  with  the  customary  method,  it  is  necessary  that  the  operator 
watch  carefully  when  making  his  valve  changes,  until  he  is  thoroughly 
accustomed  to  the  new  procedure.  He  must'  be  particularly  careful 
not  to  lea-re  the  carburetor  or  superheater  blast  valves  or  the  lower, 
hot  valve  open  while  making  the  blow-run,  or  any  of  tJie  blast  valves 
open  when  making  the  steam  run.  After  a  few  days  of  operation  the 
gas  maker  will  become  thoroughly  familiar  with  this  cycle,  and  no 
more  difficulty  will  be  experienced  in  handling  it  than  any  other  cycle. 

9.  Smoke  Prevention 
Smoke  given  off  by  a  gas  works  or  other  plant  is  of  course  much 
more  objectionable  in  some  localities  than  in  others.  Some  operators 
whose  plants  are  unfortunately  located  in  or  near  residence  districts, 
have  feared  the  creation  of  a  smoke  nuisance  from  the  use  of  bitum- 
inous coal  as  generator  fuel  more  than  any  other  objection  which  has 
been  raised  in  connection  with  it.  It  is  difficult  to  prevent  the  escape 
of  smoke  at  times  from  any  gas  plant,  regardless  of  the  fuel  used.  With 
bituminous  coal  the  possibilities  for  smoke  production  are  somewhat 
greater  than  with  coke,  but  by  arrangement  of  the  operating  condi- 
tions, it  is  possible  to  reduce  the  smoke  to  a  minimum,  if  not  entirely 
to  abolish  it.  Smoke  from  coal  in  a  water-gas  set,  as  in  boiler  plants 
or  other  furnaces,  arises, from  incomplete  combustion.  If  conditions 
are  so  adjusted  that  combustion  is  complete  at  all  times,  no  smoke 
will  be  produced.  The  greatest  smoke  difficulty  is  found  when  getting 
a  set  up  to  a  working  condition  after  a  long  layover,  and  it  follows 
that   the  difficulty   is   likely   to  be  greater   in   plants   operating  but   a 


WATER-GAS    OPERATING    METHODS  19 

small  portion  of  the  day  than  in  those  running  nearly  full  time.  If. 
after  cleaning  the  fire  in  the  morning  after  a  layover  of  several 
hours,  a  large  amount  of  green  coal  is  put  in  the  generator  and 
blasted,  the  result  is  the  evolution  of  a  large  amount  of  gas,  This 
gas  by  itself  would  perhaps  be  combustible,  but  it  is  diluted  by 
a  considerable  amount  of  carbon  dioxide  formed  during  the  early 
part  of  the  blasting  period  by  the  combination  of  air  with  the  incan- 
descent fuel  below.  Also  considerable  steam  is  produced  by  the 
decomposition  of  the  green  fuel  and  by  the  evaporation  of  surface 
moisture.  We  have,  therefore,  a  lean  gas  mixture  carrying  tarry 
vapors  passing  from  the  generator  into  the  carburetor  and  super- 
heater, and  thence  up  the  stack.  The  generator  gases  from  coke 
alone  are  difficult  to  ignite  at  the  very  beginning  of  the  blast,  but 
being  colorless  and  carrying  no  tarry  vapors,  they  are  not  noticed. 
The  problem  then  with  coal  fuel  is  to  bring  the  gases  as  soon  as 
possible  to  a  requisite  degree  of  richness,  so  that  they  will  burn. 
This  is  accomplished  if  the  temperature  of  the  generator  fuel  bed  is 
rapidly  brought  up  so  high  that  a  large  part  of  the  carbon  dioxide 
formed  in  the  combustion  zone  is  reduced  by  the  upper  layers  of  the 
incandescent  fuel,  to  carbon  monoxide.  A  deep  bed  of  incandescent 
coke  soon  produces,  upon  blasting,  combustible  gases.  The  gas 
maker  has  two  alternatives  then,  either  to  start  operation  with  coke 
and  get  the  fire  hot  and  the  generator  gases  lighted  before  charging 
any  coal,  or  if  he  desires  to  be  entirely  independent  of  coke,  he  can 
do  so  by  operating  so  that  considerable  coked  fuel  from  the  previous 
day's  run  remains  in  the  generator  after  cleaning  the  fire.  To  do  the 
latter  he  must  retain  a  fuel  reserve  from  the  preceding  daw  suffi- 
cient to  operate  on  until  the  gases  passing  from  the  generator  are 
rich  enough  to  ignite.  The  method  adopted  at  Streator,  and  found 
to  work  satisfactorily,  was  to  take  only  one  or.  two  runs  off  the  last 
coaling  before  a  layover,  and  when  no  blow-run  cycle  was  in  use,  to 
blast  the  fire  for  two  minutes  before  shutting  down.  No  steam  run 
followed  the  last  blast  in  this  latter  case.  In  this  manner  a  hot  bed 
of  fuel  was  left  beneath  the  fresh  charge  and  by  the  next  morning 
this  was  largely  converted  into  coke.  The  generator  lid  was  left 
slightly  ajar  over  night,  and  sufficient  air  entered  there  to  burn  the 
volatile  given  of!  by  the  coal.  This  helped  to  maintain  the  tempera- 
ture in  the  carburetor  and  superheater,  but  there  was  no  overheating 
of  these  chambers.  After  cleaning  the  fire  in  the  morning,  which 
usually  did  not  take  more  than  20  to  40  minutes,  a  considerable  bed 
of  fuel  remained  for  starting  operation.  This  fuel  was  blasted  about 
10  minutes.  At  the  end  of  about  1  to  5  minutes  the  gases  were  com- 
bustible, and  could  be  lighted  in  the  carburetor.      After  making  one 


20  WATER-GAS    OPERATING    METHODS 

run,  a  charge  of  coal  of  normal  size  was  made,  and  on  the  subsequent 
blast  little  or  no  difficulty  was  experienced  in  igniting  the  gases  and 
burning  up  all  or  nearly  all  of  the  smoke.  After  the  start-up  period 
but  little  difficulty  should  be  encountered  in  overcoming  the  smoke 
nuisance  if  operating  conditions  are  normal,  i.  e.,  (a)  if  the  genera- 
tor is  kept  hot  enough  to  produce  combustible  gas  during  blast, 
(b)  if  the  checker  work  is  hot  enough  to  ignite  the  mixture  of  this 
gas  with  the  secondary  air,  as  supplied  by  carburetor  blast,  and  (c) 
if  the  combustible  gas  and  carburetor  air  are  properly  mixed  and 
in  correct  proportions. 

Some  of  these  conditions  may  be  obtained,  when  lacking,  by  a 
change  in  the  operating  procedure.  For  example,  if  the  heats  in  the 
carburetor  and  superheater  are  too  low,  an  increase  in  the  amount 
of  generator  blast  or  decrease  in  the  amount  of  steam  used  during 
the  run  are  obvious  remedies.  Where  the  mixing  of  air  and  blast 
gases  in  the  carburetor  and  superheater  is  poor,  it  may  be  remedied 
in  some  cases  by  a  rearrangement  of  the  checker  work  spacing,  or 
by  some  device  in  the  secondary  air  inlets  to  carburetor  and  super- 
heater, which  will  cause  the  incoming  air  to  mix  more  intimately  with 
the  blast  gas  from  the  generator.  Such  cases  must  have  individual 
attention,  and  no  specific  suggestion  can  be  given  covering  all  cases. 

10.  Prevention  of  Sticking  of  Valves  Caused  by  Tar  Deposits 
The  gases  leaving  the  generator  when  bituminous  coal  is  used, 
consist  not  only  of  carbon  monoxide,  hydrogen,  and  carbon  dioxide, 
the  usual  constituents  of  water-gas,  but  they  also  include  varying 
amounts  of  hydrocarbons.  Some  of  these  are  permanent  gases,  but 
present  also  are  tarry  vapors.  These  vapors  are  partially  distilled  in 
their  passage  through  the  set,  and  if  condensed,  deposit  as  a  sticky 
viscous  pitch.  This  pitch  is  in  evidence  at  any  part  of  the  machine 
where  there  is  a  slight  leak,  as  for  example,  at  the  hot  valve  and  the 
carburetor  and  superheater  blast  valves,  around  the  oil  spray  stuffing 
box,  and  occasionally  at  the  generator  lid.  This  pitch  is  fairly  fluid 
when  hot,  but  when  cool  is  very  tough  and  viscous,  and  is  likely  to 
cause  valves  to  stick  very  tightly.  This  need  give  little  trouble  if 
preventive  measures  are  taken.  Usually  a  fairly  fluid  mixture  of 
lubricating  oil  and  flake  graphite,  smeared  occasionally  on  the  valve 
stems,  will  prevent  the  sticking.  Some  operators  have  obtained  bene- 
ficial results  by  tapping  a  small  hole  in  the  valve  bonnet  and  pouring 
a  little  lubricating  oil  into  the  valve  through  this  hole  once  a  day. 
In  general,  troubles  of  this  sort  are  reduced  to  a  minimum  when 
proper  temperatures  are  maintained  throughout  the  set  and  the 
weight  of  charges  is  not  excessive.  In  plants  operating  with  but 
short  layovers,  very  little  trouble  is  usually  experienced. 


WATER-GAS    OPERATING    METHODS  21 

11.     Control  of  Clinker  From   Central   District   Coals. 

Of  the  half-dozen  coals  tested  at  Streator,  none  has  given  any 
clinker  difficulties  under  the  conditions  of  operation  used  there.  Some 
coals  have  produced  decidedly  mqre  fusible  clinkers  than  others,  but 
in  all  cases  these  clinkers  have  been  brittle  and  easily  broken  up  for 
removal.  Owing  to  the  short  operating  period,  averaging  about  6.5 
running  hours  per  day,  only  one  clean  per  day  was  necessary,  and  in 
this  period  the  clinker  formed  was  of  just  about  the  proper  thick- 
ness to  be  removed  readily.  In  a  few  cases  it  was  found  that  con- 
siderable carbon  was  fused  in  with  the  clinker,  but  usually  the  clinker 
was  very  free  from  unburned  material. 

The  nature  of  the  clinker  and  the  ease  with  which  it  was  handled 
may  be  attributed  to  a  considerable  degree  to  the  blasting  and  steam- 
ing conditions  which  were  markedly  different  from  those  usually 
employed  with  coke  fuel.  The  steam  used  in  the  generator  averaged 
about  35  pounds  per  1,000  cubic  feet  of  gas  made.  This  is  somewhat 
more  than  is  ordinarily  considered  good  practice  with  good  coke.  The 
blast  pressure  maintained  under  the  grate  averaged  about  17  inches, 
and  the  amount  passing  through  the  fire,  as  indicated  by  the  air 
meter,  amounted  to  about  1,230  cubic  feet  per  1,000  cubic  feet  of  gas 
made.  This  is  decidedly  lower  than  the  amount  usually  regarded 
as  good  practice  with  coke  fuel.  It  was  possible  to  force  more  air 
through  the  fire  on  only  a  few  occasions,  owing  to  the  limited  cap- 
acity of  the  turbine  blowers  available.  Had  it  been  possible  to  force 
more  air  through  the  fire  in  a  given  time,  it  is  possible  that  the 
clinker  would  have  been  of  a  different  character;  yet  under  the  ex- 
isting conditions,  fusion  seemed  to  have  been  fairly  complete  in 
most  cases.  The  clinker  wras,  in  most  cases,  well  down  on  the  grate, 
and  there  was  little  tendency  to  the  formation  of  side  clinker  (edge- 
ings)  except  in  the  case  of  one  coal.  This  coal  gave  softer  clinker 
than  the  others,  and  fusion  was  seemingly  less  complete.  Where 
more  up  runs  than  down  runs  were  employed,  this  coal  gave  con- 
siderable side  clinker,  and  this  tendency  seemed  to  increase  with  the 
proportion  of  up  runs.  By  alternating  the  up  and  down  runs,  this 
side  clinker  did  not  form.  With  the  other  coals  it  was  the  usual 
practice  to  make  two  up  runs  after  each  coaling,  and  alternate  all 
other  runs.  Usually,  from  two  to  four  pounds  more  steam  per 
minute  were  used  on  up  runs  than  on  down  runs.  In  general,  it  may 
be  said  that  with  coal  fuel  under  all  conditions  of  operation  tried, 
the  clinker  was  much  more  easily  handled  than  that  from  the  retort 
coke  formerly  employed,  which  was  made  from  a  Marian  County, 
Kentucky,  coal.     In  mixing  fuels  there  is  a  possible  difficulty   which 


22  WATKR-GAS    OPERATING    METHODS 

may  or  may  not  be  encountered,  namely,  the  formation  of  a  clinker 
from  the  mixed  ashes,  much  more  difficult  to  handle  than  the  clinker 
from  either  of  the  components.  This  phenomenon  has  been  observed 
in  some  plants  and  seems  entirely  logical.  The  formation  of  clinker 
is  a  chemical  as  well  as  a  physical  process,  and  the  constituents  pres- 
ent in  the  ashes  of  two  fuels  may  form  a  combined  clinker  which  is 
extremely  obstinate.  In  the  tests  at  Streator  the  coke  used,  which 
was  retort  coke  from  Harlan  County  (Kentucky)  coal,  was  con- 
siderably more  difficult  to  handle  than  the  clinker  from  Illinois  coal, 
but  the  mixture  produced  a  clinker  which  seemed  to  lie  somewhere 
between  the  two  in  workability,  as  though  the  coal  ash  added  com- 
ponents which  made  the  clinker  more  brittle.  Only  experiments 
with  a  given  mixture  of  fuels  could  determine  what  the  outcome  in 
a  particular  case  would  be.  So  little  is  yet  known  about  the  relation 
of  ash  composition  to  fusibility,  or  even  about  the  relation  of  fusi- 
bility to  clinker  formation  in  practical  operation  of  a  water-gas  set, 
that  we  have  nothing  to  guide  us  in  the  selection  of  coals  or  mix- 
tures so  far  as  clinkering  properties  are  concerned  except  actual 
trials  on  a  commercial  scale. 

The  clinker  formed  when  operating  with  a  blow-run  may  be 
quite  different  from  that  obtained  with  the  ordinary  method  of  opera- 
tion, this  difference  being  due  primarily  to  the  difference  in  tempera- 
tures prevailing  with  and  without  the  blow-run,  which  has  been 
described  previously  in  this  bulletin.  This  difference  in  character  of 
the  ash  or  clinker  has  a  marked  effect  on  the  hourly  output,  which 
is  more  pronounced  as  the  day  proceeds.  If,  for  example,  a  coal  is 
used  which  does  not  readily  form  a  clinker,  or  whose  ash  is  not 
readily  fusible,  it  may  happen  that,  with  the  usual  blast  employed  with- 
out a  blow-run,  no  solid  clinker  will  form.  In  this  case  ashes  will 
accumulate  and  in  much  greater  volume  than  that  occupied  by  clinker. 
As  the  volume  of  ash  increases,  there  is  of  course  less  incandescent 
fuel  in  the  generator,  and  what  is  commonly  called  a  "cold  generator" 
is  the  result.  With  this  lower  temperature  in  the  generator,  the  caking 
and  matting  of  the  generator  fuel  is  more  troublesome. 

The  effect  of  the  accumulation  of  ashes,  along  with  an  increased 
tendency  of  the  coal  to  cake  and  mat  together,  is  an  increase  in  the 
resistance  of  the  fuel  body  to  the  passage  of  air  when  blasting.  This 
results  in  a  further  decrease  in  the  temperature  in  the  generator.  With 
this  condition  it  will  be  found  that  the  fire  will  need  cleaning  oftener, 
and  the  make  per  hour,  or  make  per  run,  will  rapidly  decrease  after  a 
few  hours  running. 


WATER-GAS    OPERATING     METHODS  23 

'I. his  same  coal  may  be  used  with  more  blast,  or  with  the  blow-run 
■method  of  operating,  and  form  a  clinker  which  will  occupy  consider- 
ably less  space.  The  matting  is  less  troublesome  with  the  increase  in 
temperature  in  the  generator,  and  the  make  per  run  does  not  decrease 
till  much  later  in  the  day,  and  after  considerably  more  gas  has  been 
made. 

SUGGESTIONS  FOR  OPERATIXd  WITH  COAL  FUEL 
It  is  impossible  to  lay  down  rules  for  operation  which  will  apply 
in  all  cases.  The  operator  beginning  the  use  of  coal  must  experiment  a 
little  to  rind  the  conditions  which  best  apply  to  his  individual  case. 
The  following  suggestions  are  presented  as  a  guide  and  were1  appli- 
cable to  the  conditions  at  Streator. 

1.  It  is  well  to  begin  operation  with  about  50  per  cent  coal,  grad- 
ually increasing  the  percentage  of  coal  in  the  mixture. 

2.  Select  a  coal  low  in  sulphur.  Most  plants  are  not  equipped  to 
handle  more  sulphur  in  the  gas  than  will  be  produced  by  1.5  per  cent 
sulphur  in  the  coal.  There  are  several  central  district  coals  having 
sulphur  percentages  lower  than  this.2 

3.  The  coal  should  not  be  too  line.  It  should  preferably  be  in 
lumps  about  I  by  <>  inches  in  size.  Very  line  material  should  be 
excluded  by  forking  the  coal  with  the  usual  coke  fork. 

1.  When  starting  in  the  morning  do  not  make  double  charges  ol 
coal.  This  will  result  in  caking  and  arching,  and  the  result  will  be  a 
cold  generator,  difficult  to  bring  up  to  heal,  usually  with  excessive 
smoke  production.  It  is  better  to  have  left  a  deep  fuel  bed  by  making  a 
large  charge  shortly  before  shutting  down  the  night  before.  In  this 
case  the  carburetor  can  be  lighted  and  a  run  made  before  charging  an\ 
coal.  This  wall  give  a  quicker  start,  diminish  the  smoke,  and  resull 
in  a  larger  make  from  the  start. 

5.  Build  up  the  generator  lire  by  coal  charges  of  normal  size  (the 
same  weight  as  when  using  coke).  Make  the  charges  at  intervals  of 
say  two  runs  until  the  lire  is  up  to  the  usual  working  height,  that  is, 
just  below  the  take-off  connection,  then  charge  at  intervals  of  about 
five  or  six  runs.  Make  the  charges  as  rapidly  as  possible,  to  avoid 
loss  of  time. 

6.  Proportion  the  up  and  down  runs  and  the  steam  ttsed  .so  that 
the  clinker  wall  come  dowai  to  the  grate  where  it  can  be  readily 
removed.  The  proportion  can  best  be  determined  by  trial.  At  Strea- 
tor most  of  the  coals  did  best  with  three  up  runs  to  two  down  tuns. 
Usually  two  successive  up  runs  were  made  after  charging.  In  souk 
cases,  alternate  up  and  down  runs  seemed  more  satisfactory. 


2  Cady,  <;.  II..  Low-sulphur  coals  of  the  central  district  :    Illinois   Mining    [n\ 
tig-ation   Mull    23.   1919 


24 


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WATER-GAS    OPERATING   METHODS  25 

7.  The  length  of. blowing  and  steaming  times  will  depend  upon 
the  blast  and  steam  available.  In  general,  try  to  so  proportion  the 
blow  and  run  that  the  generator,  carburetor,  and  superheater  will 
attain  the  proper  working  temperatures  at  the  same  time.  With  coal 
there  is  a  tendency  for  the  carburetor  and  superheater  to  become  too 
hot  before  the  generator  is  hot  enough.  This  is  usually  partly  over- 
come by  one  or  more  of  the  following  methods:  (a)  By  allowing 
some  gas  to  burn  at  the  stack;  (b)  by  over-steaming  the  generator 
and  thereby  diminishing  the  amount  of  combustible  gas  formed  (this, 
however,  cools  the  generator  still  more)  ;  (c)  by  over-blowing  the 
carburetor  and  superheater;  and  (d)  by  the  use  of  the  blow-run  cycle. 
Of  these  methods,  the  writers  believe  that  (d)  is  the  most  economical 
and  results  in  the  largest  set  capacity.  If  this  cycle  is  not  desired,  then 
the  use  of  (c)  or  (a)  seems  generally  the  least  objectionable,  where 
conditions  permit. 

8.  It  is  usually  most  .satisfactory  m  the  long  run  to  use  reduced 
steam  and  oil  during  the  first  four  or  five  runs,  while  bringing  up  the 
heats. 

9.  When  adopting  the  blow-run  method,  care  should  be  taken  to 
make  the  blow-run  of  only  sufficient  length  to  maintain  the  proper  heat 
balance  in  the  set  and  to  obtain  the  desired  make  of  gas  without  an 
excessive  expenditure  of  oil. 

10.  Be  sure  that  the  lower  hot   valve  and  carburetor  and   super 
heater  blast   valves  are  closed  before   shutting  the   stack   cap  to  make 
the  blow-run.     Do  not  reverse  the  hot  valves  while  making  the  blow- 
run.     Close  the  generator  blast    valve  before  turning  on   the   steam   to 
make  the  regular  steam  run. 

11.  It  the  carburetor  and  superheater  remain  cold  when  the  blow 
run  cycle  is  used,  make  sure  that  they  are  not  being  over  blown  during 
the  blast  period.  Use  only  enough  carburetor  and  superheater  blast 
to  burn  the  combustible  gases  in  the  set.  It  niav  be  advisable  to 
lengthen  the  blow  and  increase  tin-  amount  of  steam,  rather  than 
shorten  the  blow-run.  if  capacity  is  desired. 

L2-.  There  is  considerably  more  tar  produced  with  coal  than  with 
coke  fuel.  The  average  increase  has  not  been  ascertained,  (arc 
should  be  taken  that  the  tar  is  removed  from  the  gas  before  it  reaches 
the  purifiers.  The  operation  of  the  tar  extractor,  or  shavings  scrubber. 
especially  should  be  watched. 

L3.  The  flanges  on  the  bottoms  of  the  hot  valves  should  be 
removed  occasionally  to  remove  any  deposits  of  carbon  or  carbonized 
tar.  The  presence  of  such  deposits  is  indicated  by  the  failure  of  the 
valves  to  close  tightly. 


26  WATER-GAS    OPERATING     MKTHODS 

14.  During  layover  periods,  it  is  usually  advisable  to  leave  the 
generator  lid  slightly  open  or  "cracked."  This  seems  to  assist  in  heat- 
ing the  generator  and  in  burning  off  any  carbon  which  may  have  been 
deposited  in  the  checkerwork  of  the  carburetor  and  superheater. 

15.  There  is  a  tendency  for  hot  valves  and  oil  spray  stems  to 
stick  during  layover  periods.  This  may  be  remedied  by  smearing  the 
stems  with  a  mixture  of  lubricating  oil  and  graphite.  The  introduction 
of  oil  into  the  hot  valve  bonnets  also  seems  to  assist. 

1(>.  A  tendency  is  noticeable  for  the  fuel  to  burn  down  more 
rapidly  around  the  generator  wall  than  in  the  center.  In  order  to  avoid 
the  by-passing  of  air  and  steam  between  the  fuel  and  the  generator 
wall,  and  to  equalize  the  rate  of  subsidence  of  the  surface  of  the  fuel 
bed,  the  use  of  a  fuel  spreader  when  charging,  is  recommended, 
especially  in  the  operation  of  the  larger  sets 

CONCLUSIONS 

The  operating  conditions  with  coal,  which  have  been  described, 
have  been  adopted  for  regular  operation  in  the  Streator  plant.  The 
use  of  coal  in  that  plant  is  preferred,  not  only  by  the  superintendent, 
but  also  by  the  operating  force,  since  it  has  proven  for  that  plant 
economically  advantageous,  has  given  a  larger  hourly  output  than  the 
coke  formerly  used,  and  has  actually  made  working  conditions  easier 
for  the  men  employed,  and  has  given  the  superintendent  the  oppor- 
tunity to  accomplish  more  repairs  and  yard  work  with  the  same  force. 

The  small  size  of  the  Streator  plant  and  the  large  over-capacity 
of  its  generating  equipment  make  a  prediction  of  fuel  and  oil  efficien- 
cies attainable  in  a  larger  plant  operating  near  its  capacity  very  diffi- 
cult, if  not  impossible.  This  was  recognized  from  the  beginning  of 
the  tests.  The  plant  is  actually  making  gas  only  slightly  over  one- 
fourth  of  the  24-hour  day.  During  the  layover  periods,  a  certain 
amount  of  fuel  is  being  consumed  without  any  return  in  gas  made ; 
this  makes  the  fuel  per  1,000  cubic  feet  of  gas  relatively  high.  Like- 
wise, the  set  must  be  brought  up  to  working  condition  after  a  layover ; 
this  involves  excessive  fuel  consumption  and  reduces  the  oil  efficiency, 
since  the  oil  can  not  be  properly  fixed  until  the  temperature  in  the 
fixing  chambers  is  suitable.  This  usually  consumes  an  hour  or  so, 
which  is  a  very  large  percentage  of  the  working  day. 

Y\  Tile  these  deficiencies  in  a  test  of  this  kind  are  recognized,  the 
investigations  have  served  to  show  operating  methods  and  tendencies, 
to  indicate  the  availability  of  certain  central  district  coals  for  this 
purpose,  and  to  indicate  to  a  certain  extent  what  may  be  expected  on 
a  larger  scale  operation.  The  results  actually  obtained  and  the  details 
of  operation,  including  chemical  studies  of  various  stages  of  the  pro- 
cess, will  appear  in  a  later  publication. 


WATER-GAS    OPERATING    METHODS  27 

It  is  hoped  that  experimental  work  may  be  undertaken  in  the 
near  future  at  a  plant  operating  nearer  full  capacity,  in  order  that  all 
the  possibilities  of  coal  as  generator  fuel  may  be  realized.  In  the 
meantime  it  is  hoped  that  gas  operators  may  be  encouraged  to  try  the 
methods  outlined  in  this  paper  in  their  own  plants.  The  writers  of 
this  paper  will  be  pleased  to  render  any  assistance  possible  to  those 
requiring  it. 

ACKNOWLEDGMENTS 

Acknowledgments  are  due  to  the  Public  Service  Company  of 
Northern  Illinois  and  especially  to  Mr.  C.  W.  Bradley,  its  engineer, 
and  Mr.  James  Carswell,  superintendent  of  the  Streator  plant,  for 
assistance  given  in  carrying  out  the  work  discussed  in  this  paper. 


PUBLICATIONS  OF 
ILLINOIS  MINING  INVESTIGATIONS. 


Bulletin  1. 

Bulletin  3. 

Bulletin  10. 

Bulletin  11. 

Bulletin  14. 

Bulletin  15. 

Bulletin  16. 

Bulletin  17. 

Bulletin  18. 

Bulletin  20. 

Bulletin  21. 

Bulletin  22. 

Bulletin  23. 

Bulletin  2!t. 


ILLINOIS  STATE  GEOLOGICAL  SURVEY  DIVISION 
URBANA.  ILLINOIS 

Preliminary  report  on  organization  and  method  of  investigations,  1913. 

Chemical  study  of  Illinois  coals,  by  8.  W.  Parr,  1916. 

Coal  resources  of  District  I   (Longwall),  by  G.  H.  Cady,  1915. 

Coal  resources  of  District  VII,  by  Fred  H.  Kay,  1915. 

Coal  resources  of  District  VIII  (Danville),  by  Fred  H.  Kay  and  K.  D. 

White,  1915. 
Coal  resources  of  District  VI,  by  G.  H.  Cady,  1916. 
Coal  resources  of  District  II  (Jackson  Co.),  by  G.  H.  Cady,  1917. 
Surface  subsidence  in  Illinois  resulting  from  coal  mining,  by  Lewis  B. 

Young,  1916. 
Tests   on   clay  materials   available   in   Illinois   coal  mines,   by   R.    T. 

Stull  and  R.  K.  Hursh,  1917. 
Carbonization  of  Illinois  coals  in  inclined  gas  retorts,  by  F.  K.  Ovitz, 

1918. 
The  manufacture  of  retort  coal-gas  in  the  central  states,  using  low- 
sulphur  coal  from  Illinois,  Indiana,  and  western  Kentucky,  by  W. 

A.  Dunkley,  and  W.  W.  OdeU,  1918. 
Water-oas    manufacture    with    central    district    bituminous    coals    as 

generator  fuel,  by  W.  W.  Odell  and  W.  A.  Dunkley,  1918. 
Mines  producing  lotv-sulphur  coal  in  the  central  district,  by   Q    H. 

Cady,  1919. 
Water-gas  operating  methods  with  central  district   bituminous   coals 

as  generator  fuel.     A   summwy  of  experiments   on  a  commercial 

scale,  by  W.  A.  Dunkley  and  W.    W.   Odell,  1919. 


Bulletin 

o 

Bulletin 

4. 

Bulletin 

5. 

Bulletin 

6 

Bulletin 

7. 

Bulletin 

8 

Bulletin 

9 

Bulletin 

12 

Bulletin 

13. 

Bulletin 

91 

Bulletin  100 

ENGINEERING  EXPERIMENT  STATION 
URBANA.  ILLINOIS 

Coal  mining  practice  in  District  VIII  (Danville),  by  S.  O.  Andros,  191S. 

Coal  mining  practice  in  District  VII,  by  S.  O.  Andros,  1914. 

Coal  mining  practice  in  District  I  (Longwali),  by  S.  O.  Andro9,  1914. 

Coal  mining  practice  in  District  V,  by  S.  O.  Andros,  1914. 

Coal  mining  practice  in  District  IT,  by  S.  O.  Andros,  1914. 

Coal  mining  practice  in  District  VI,  by  S.  O.  Andros,  1914. 

Coal  mining  practice  in  District  III,  by  S. 

Coal  mining  practice  in  District  IV,  by  S. 

Coal  mining  in  Illinois,  by  S.  O.  Andros, 

all  the  district  reports. ) 
Subsidence  resulting  from  mining,  by  L.  E.  Young  and  H.  H.   Stoek, 

1916. 
Percentage  of  extraction  of  bituminous  coal  with  special  reference  to 

Illinois  conditions,  by  C.  M.  Young,  1917. 


O.  Andros,  1915. 
O.  Andros,  1915. 
1915.      (Complete  resume  of 


U.  S.  BUREAU  OF  MINES 
WASHINGTON.  D.  C. 

Bulletin    72.     Occurrence  of  explosive  gases  in  coal  mines,  by  N.  H.   Darton,  1915. 

Bulletin    83.     The  humidity  of  mine  air,  by  R.  Y.  Williams,  1914. 

Bulletin    99.     Mine  ventilation  stoppings,  by  R.  Y.  Williams,  1915. 

Bulletin  102.     The  inflammability  of  Tllinos  coal  dusts,  by  J.  K.  Clement  and  D.  A. 

Scholl,  Jr.,  1916. 
Bulletin  137.     Use  of  permissible  explosives  in  the  coal  mines  of  Illinois,  by  J.  R. 

Fleming  and  J.  W.  Koster,  1917. 
Bulletin    138.     Coking  of  Illinois  coals,  by  F.  K.   Ovitz,  1917. 
Technical  Paper  190.     Methane   accumulations   from   Interrupted   ventilation,    with 

special  reference  t©  coal  mines   in  Illinois  and  Indiana,  by  H.   I. 

Smith  and  Robert  J.  Hamon,  1918. 
1  Bulletins  listed  in  italics  apply  directly  to  the  problem  of  use  of  central  dis- 
trict bituminous  coals  in  place  of  eastern  coal  and  coke. 


